1. Download Switch Video Combiner https://bramantya.org/apps/ (updates will be posted there, feel free to mirror)
2. Copy the program to the same folder as the videos you want to combine
3. run the program. The combined video will be inside COMBINED folder.

Made with WinRAR self-extractor, FFMPEG, and googling (actually, duck-duck-go-ing) a bunch of scripts other people have made.